Effects of soybean oligosaccharides instead of glucose on growth, digestion, antioxidant capacity and intestinal flora of crucian carp cultured in biofloc system

Abstract

This study aimed to investigate the effects of soybean oligosaccharide-cultured biofloc on the growth, digestion, antioxidant capacity, and intestinal flora of crucian carp. Glucose as a carbon source was used as the control group (Con), and glucose was replaced with soybean oligosaccharides by 1 % (S1), 5 % (S5), 10 % (S10), and 100 % (S100) with C: N of 15 as the experimental group with six replicates. Compared with the Con group, the accumulation of nitrate nitrogen (NO3--N) decreased significantly (P < 0.05), and the turbidity (T·d) of water increased significantly in the S100 group. The biofloc volume (FV), weight gain (WG), and specific growth rate (SGR) were significantly increased (P < 0.05), and the feed coefficient (FCR) was significantly decreased (P < 0.05) in the S1 group. The content of malondialdehyde (MDA) in the S10 and S100 groups was significantly decreased (P < 0.05). Intestinal amylase in S10 and S100 groups was significantly decreased (P < 0.05), the lipase was significantly increased in the S10 group (P < 0.05), and the trypsin was significantly increased in the S1 and S5 groups (P < 0.05). In addition, the Chao index of intestinal microbial species richness was significantly increased in the S1 group (P < 0.05). The abundance of Pseudomonas and Vibrio decreased significantly in the S5 and S10 groups (P < 0.05). The pathways related to metabolic activities in intestinal flora in the experimental groups were significantly up-regulated (P < 0.05). Our results showed that the growth and digestion capacity of crucian carp could be improved in the biofloc system cultured by 1–5 % soybean oligosaccharides replacement of glucose, the abundance of beneficial bacteria such as Actinobacteriota in the intestine could be increased, and the abundance of harmful bacteria such as Pseudomonas and Vibrio could be decreased.